New cosmetic formulations are increasingly viscous or contain solid components that are difficult or impossible to dispense using existing technology. Simultaneously, there exists a growing demand for cosmetic formulations with physiologically active components. But such components are often unstable in consumer products.
One response to the first problem has been to design mechanical pump dispensers that can handle today's more viscous products. To date, the results have not been encouraging. Mechanical micropumps can be of the traditional or so-called "airless" types, and are well known. See, for example, U.S. Pat. Nos. 3,001,524; 3,452,905; 4,892,232; 4,9303,999; 5,096,097; 5,183,187; 5,566,865.
One type of piston dispenser relies on an airless micropump mechanism to force flowable material out of a reservoir. On the return stroke of the pump mechanism a vacuum is created inside the reservoir. In response to the reduced pressure inside the reservoir, flowable material from the primary container moves into the reservoir, and simultaneously, the piston is pulled toward the reservoir, thus reducing the volume between the piston and the intake of the reservoir. With this type of device, and in the traditional non-airless pumps, only comparatively thin products can be made to flow because insufficient negative pressure is created inside the reservoir.
Furthermore, micropumps, because of the several small and delicate components of which they are comprised, are subject to failure of various types. The most common of these, perhaps, is leakage. Commonly, leakage may occur through the stem of the pump as a result of poor fit between the piston and the stem. Leakage may also occur from around the stem of the pump as a result of poor fit between the piston and the housing.
Poor fit between the components may be a result of the difficulties of holding to tolerance in manufacturing or it may be due to creep of the molded components before reaching a final set after manufacturing. Poor fit of the components may also be due to degradation of the components as a result of exposure to various elements, i.e. heat, cold, and chemical attack by the product.
In another piston-type dispensing device, a relatively high pressure region is located behind the piston. When the exit valve for the product is opened, the piston is driven by the pressure gradient and product is forced out of the open valve.
The primary disadvantages here are the hazards of manufacturing, transporting, storing, using and disposing of pressurized containers. Because of these hazards there are also limitations on the container materials and construction.
Furthermore, performance characteristics may suffer with this type of package. Specifically, as the pressure inside the container decreases with use, the dispensing characteristics deteriorate. Toward the end of the life of the package, product is dispensed slowly and weakly, creating an unfavorable impression on the consumer. Sometimes all of the pressure will be lost before the contents of the package are used up. Also, this type of package is subject to leaking as a result of constant pressure on the sealing surfaces of the package.
Other piston-type dispensers rely on mechanical pressure applied directly or indirectly to the piston. U.S. Pat. No. 5,513,778 discloses a dispenser for viscous fluid products that is operated by applying direct manual pressure to the piston, which is accessible through an opening on the bottom of the outer body. French Patent No. 2,721,907 discloses a cosmetic product dispenser for cream products in which the piston rides on a screw-threaded shaft when the shaft is rotated. This is an example of a piston that is activated by indirect pressure.
The '778 design is simple with few interrelated parts. Its disadvantages include the following: it requires two hands to operate; the piston disappears into the package making it inconvenient to apply pressure to the bottom of the piston; the force applied to the piston can result in the uncontrolled movement of the piston when static friction is suddenly overcome, resulting in a excessive dosing.
Dispensers that use indirect pressure such as the '907 design, are more complicated because a means of engagement must be supplied to transfer the applied pressure through the package to the piston. This increased complexity in design is disadvantageous in manufacturing, cost and use. This design also requires two hands to operate.
In response to the second problem, systems have been devised that allow the active components to be stored separately from the rest of the formulation. The consumer could then mix the components just prior to use. This system relies on the consumer mixing the components and doing so in the right proportions. More user friendly systems have the components mix just prior to, or upon exiting the container.
In such a typical configuration, two micropump devices or two pre-pressurized devices are ganged together and actuated by one actuator that fits over both valve stems. In practice, the results have not been satisfactory. In part, this is because of variations in the dispensed quantity from mechanism to mechanism. In the best cases, variations in a sample of like components dispensing the same product will be about 20%. Often the difference is greater. This means that unequal quantities of the two products are being dispensed.
Furthermore, this type of multi-dispenser does not perform well if the viscosities of the different products vary widely. The same micropump will have different dispensing characteristics for products with different theological properties, say, viscosity. This introduces additional variation in the relative quantity of the simultaneously dispensed products. This problem is made worse by uneven application of pressure on the actuator. If pressure is not transferred evenly to each valve stem, then each piston will not move the same distance, causing unequal dispensing of the two products.
Uneven use-up of the products is a serious drawback for at least two reasons. Firstly, the products were meant to be used together, but since one product will be used up before the other this becomes impossible. But even before any one of the products has been used up, the relative amount of each product in any one application will vary widely. In some cases this will render the combined product ineffective or give undesirable results. This is particularly true in treatments where one product activates the other or a desired reaction of the dispensed products is sought.
Another multi-dispenser is disclosed in French Patent No. 2,721,907. Here, a single composite piston fits into a double-barreled container, and advances along both barrels via a screw-threaded rotating shaft to dispense the products. This design is comparatively complex, involving a screw-threaded mechanism, requires two hands to operate, and is limited to two separate product components.
U.S. Pat. No. 5,076,298 discloses a dispenser for multi-component hair cosmetics in which separately stored product components are transferred by capillary action, from their separate containers and into tines made of absorbent material, where the components mix, just prior to use. This design, relying as it does on capillary activity, is suitable only for thin, non-viscous products.
There is then, a growing demand in the personal care markets for a device that can reliably dispense multiple components in any desired ratio of volume, keeping the components separated until just prior to use. Also, a reliable dispensing device is needed for simultaneously dispensing multiple components when the viscosities of the multiple components are significantly different from each other. Furthermore, a device that can reliably dispense products of relatively high viscosity is needed.
None of the limitations discussed above is found in the present invention. The present invention does not rely on pre-pressurized contents. Nor does the present invention rely on small, delicate components to create fluid movement indirectly via a vacuum. There are no small, delicate parts susceptible to the kinds of failure discussed above. The number of parts is comparatively few. There is only one type of sealing interface which means that only one fitment requires precise tolerance. The present invention can be operated with one hand. The pressure surface does not disappear into the package making it difficult to dispense product. No accidental excessive dosing, nor uneven dosing is possible. More than two components may be separated prior to use. The device may be designed to dispense different predetermined quantities of the different products, thus ensuring the correct proportions of each product.
Some of the limitations just noted are avoided by using a ratchet design. This design allows for dosing a prefixed amount of product, prevents excessive dosing by providing a positive stop, and returns the pressure surface to its initial position for subsequent uses. There are many ratcheting dispensers with diverse mechanisms of operation. Many involve numerous pins, springs, clamps and support racks. None meets the criteria of being simple in design, containing few parts, and using a single ratchet support column to simultaneously dispense multiple products.
Accordingly, a main object of the invention is to provide an improved multi-dispenser which overcomes the disadvantages of known multi-dispensing devices, having simplified construction and being convenient to use.
Another object of the present invention is to provide an improved dispensing device that can simultaneously dispense two or more materials whose viscosities differ from one another significantly.
Another object of the present invention is to provide an improved dispensing device that can simultaneously dispense different predetermined quantities of two or more materials.
Another object of the present invention is to provide an improved dispensing device that can dispense a measured amount of materials of relatively high viscosity.